There is a technology called augmented reality (AR), with which an image of the real space is added with an image corresponding to the real space. With the AR, a camera or others are used to obtain an image of the real space, and with respect to the obtained image of the real space, virtual information (hereinafter, virtual information) is superimposed for display. By viewing the displayed virtual information superimposed with respect to the real space, a user recognizes an object displayed as the virtual information as if it exists in the real space.
The AR includes marker AR and marker-less AR.
With the marker AR, image information is registered in advance about a marker physically disposed in the real space (for example, a colored square of a predetermined size). An image of the real space (real image) is obtained by imaging of the real space, a marker is detected from this real image, and using information about the size and angle of the detected marker, for example, the spatial position relationship of an imaging apparatus with respect to the marker is calculated. Based on this spatial position relationship of the imaging apparatus with respect to the marker, the display position and the display angle of the virtual information are calculated. Based on the calculated display position and display angle, the virtual information is displayed on a display apparatus whose position is fixed relative to the imaging apparatus so that the user can perceive the virtual information together with the real space (for example, see Patent Literature 1.).
On the other hand, with the marker-less AR, no specific marker is used. Any object in a real image and the real space itself are spatially recognized, and based on information about the size, the angle, and others of the object, for example, the spatial position relationship of the imaging apparatus with respect to the object is calculated. Based on the position relationship, the display position and the display angle of the virtual information are calculated, and the virtual information is displayed on a display apparatus whose position is fixed relative to the imaging apparatus so that the user can perceive the virtual information together with the real space.